The present invention relates to vehicle seat assemblies and in particular to vehicle seat assemblies having an linear actuator for use as a seat adjuster and/or a recliner.
Manually adjustable vehicle seat assemblies typically include an adjuster for adjusting the fore and aft position of seat assembly relative to the vehicle and a recliner for adjusting the inclination of the seat back. Such mechanisms must be capable of withstanding the high loads that may be applied to the seat assembly during a vehicle collision. More and more vehicle seat assemblies are being developed with the seat belts mounted directly on the seat assembly rather than being mounted to the vehicle structure. This increases the seat belt comfort because the belt anchors are moved with the seat assembly during adjustment rather than being fixed to the vehicle structure. However, with the seat belts mounted to the seat assembly, the forces applied to the recliner and adjuster mechanisms during a vehicle collision are significantly increased.
Accordingly, it is an object of the present invention to provide a recliner mechanism and a seat adjuster mechanism that are capable of withstanding seat belt loads.
It is a further object of the present invention to provide such devices which, when under high loading conditions, act to "lock up", making relative movement of seat components more difficult as opposed to failing under the high loads in a manner which increases the likelihood of seat component movement.
It is a feature of the present invention to provide a seat assembly with a seat adjuster mechanism or a recliner mechanism which relies upon friction to lock the movable seat components in place. When loaded, the mechanisms are designed to increase the normal force at the friction surfaces, thereby increasing the friction holding the seat components in place.
It is a further feature of the invention that the actuator of the present invention is infinitely variable in some embodiments to allow adjustment to any position desired.
The actuator includes a first part attached to one of the seat assembly components in the form of a lead screw with an external helical screw thread. A second part is attached to another seat component that is movable relative to the component attached to the first part. This second part includes an spin nut having a threaded bore that is threaded onto the lead screw and a housing for axially capturing the spin nut. The housing includes an end cap that is axially movable between a lock position in which the axial end walls of the spin nut are frictionally engaging the cap and the housing to prevent rotation of the nut along the lead screw and a release position in which the spin nut is freed for rotation. The end cap movement is controlled by a cam engaging an outer surface of the cap and an internal spring urging the end cap away from the housing.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.